From: Ravi Bangoria <ravi.bangoria@amd.com>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: Stephane Eranian <eranian@google.com>,
Slade Watkins <srw@sladewatkins.net>,
linux-perf-users <linux-perf-users@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Ian Rogers <irogers@google.com>,
Namhyung Kim <namhyung@gmail.com>,
Kees Cook <keescook@chromium.org>,
sandipan.das@amd.com, Bill Wendling <morbo@google.com>,
clang-built-linux <llvm@lists.linux.dev>,
Yonghong Song <yhs@fb.com>, Peter Zijlstra <peterz@infradead.org>,
Ravi Bangoria <ravi.bangoria@amd.com>
Subject: Re: Invalid event (cycles:pp) in per-thread mode, enable system wide with '-a'.
Date: Mon, 26 Jun 2023 11:14:22 +0530 [thread overview]
Message-ID: <5c077e61-c206-812f-1cb9-d47785e8176f@amd.com> (raw)
In-Reply-To: <CAKwvOdmY7qoSG61f7UouWFz+gNN531FhpHbqawrAKCNKNDJHnw@mail.gmail.com>
Hi Nick,
On 23-Jun-23 9:53 PM, Nick Desaulniers wrote:
> On Tue, Oct 11, 2022 at 10:05 PM Ravi Bangoria <ravi.bangoria@amd.com> wrote:
>>
>> On 12-Oct-22 9:36 AM, Ravi Bangoria wrote:
>>> On 12-Oct-22 3:02 AM, Nick Desaulniers wrote:
>>>> On Thu, Oct 6, 2022 at 8:56 PM Ravi Bangoria <ravi.bangoria@amd.com> wrote:
>>>>>
>>>>> +cc: PeterZ
>>>>>
>>>>>>>>>> +Ravi who may be able to say if there are any issues with the precise
>>>>>>>>>> sampling on AMD.
>>>>>>>>>
>>>>>>>>> Afaik cvcles:pp will use IBS but it doesn't support per-task profiling
>>>>>>>>> since it has no task context. Ravi is working on it..
>>>>>>>>
>>>>>>>> Right.
>>>>>>>> https://lore.kernel.org/lkml/20220829113347.295-1-ravi.bangoria@amd.com
>>>>>>>
>>>>>>> Cool, thanks for working on this Ravi.
>>>>>>>
>>>>>>> I'm not sure yet whether I may replace the kernel on my corporate
>>>>>>> provided workstation, so I'm not sure yet I can help test that patch.
>>>>>>>
>>>>>>> Can you confirm that
>>>>>>> $ perf record -e cycles:pp --freq=128 --call-graph lbr -- <command to profile>
>>>>>>>
>>>>>>> works with just that patch applied? Or is there more work required?
>>>>>>> What is the status of that patch?
>>>>>>>
>>>>>>> For context, we had difficulty upstreaming support for instrumentation
>>>>>>> based profile guided optimizations in the Linux kernel.
>>>>>>> https://lore.kernel.org/lkml/CAHk-=whqCT0BeqBQhW8D-YoLLgp_eFY=8Y=9ieREM5xx0ef08w@mail.gmail.com/
>>>>>>> We'd like to be able to use either instrumentation or sampling to
>>>>>>> optimize our builds. The major barrier to sample based approaches are
>>>>>>> architecture / micro architecture issues with sample based profile
>>>>>>> data collection, and bitrot of data processing utilities.
>>>>>>> https://github.com/google/autofdo/issues/144
>>>>>>
>>>>>> On existing AMD Zen2, Zen3 the following cmdline:
>>>>>> $ perf record -e cycles:pp --freq=128 --call-graph lbr -- <command to profile>
>>>>>>
>>>>>> does not work. I see two reasons:
>>>>>>
>>>>>> 1. cycles:pp is likely converted into IBS op in cycle mode.
>>>>>> Current kernels do not support IBS in per-thread mode.
>>>>>> This is purely a kernel limitation
>>>>>
>>>>> Right, it's purely a kernel limitation. And below simple patch on top
>>>>> of event-context rewrite patch[1] should be sufficient to make cycles:pp
>>>>> working in per-process mode on AMD Zen.
>>>>>
>>>>> ---
>>>>> diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
>>>>> index c251bc44c088..de01b5d27e40 100644
>>>>> --- a/arch/x86/events/amd/ibs.c
>>>>> +++ b/arch/x86/events/amd/ibs.c
>>>>> @@ -665,7 +665,7 @@ static struct perf_ibs perf_ibs_fetch = {
>>>>>
>>>>> static struct perf_ibs perf_ibs_op = {
>>>>> .pmu = {
>>>>> - .task_ctx_nr = perf_invalid_context,
>>>>> + .task_ctx_nr = perf_hw_context,
>>>>>
>>>>> .event_init = perf_ibs_init,
>>>>> .add = perf_ibs_add,
>>>>> ---
>>>>>
>>>>> [1]: https://lore.kernel.org/lkml/20220829113347.295-1-ravi.bangoria@amd.com
>>>>
>>>> Hi Ravi,
>>>> I didn't see the above diff in
>>>> https://lore.kernel.org/lkml/20221008062424.313-1-ravi.bangoria@amd.com/
>>>> Was there another distinct patch you were going to send for the above?
>>>
>>> Yes Nick. I was planning to send it once the rewrite stuff goes in.
>>
>> Hi Nick,
>>
>> Since you have practical use case, would it be possible to run your workflow
>> with perf rewrite and IBS patches applied? It will help us in finding/fixing
>> more bugs and upstreaming these changes.
>
> Hi Ravi,
> Sorry, I'm not able to load a custom kernel image on my employer
> provided workstation, and I never got approval to expense hardware for
> testing this otherwise.
>
> Was there ever any update on this? I'm on 6.1.25 now and still cant run
> $ perf record -e cycles:pp --call-graph lbr <any command to profile>
Per-process precise sampling on AMD platforms should work from 6.2-rc1
onward. However, --call-graph=lbr is not supported on AMD (hw limitation).
Thanks,
Ravi
next prev parent reply other threads:[~2023-06-26 5:45 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-29 21:54 Invalid event (cycles:pp) in per-thread mode, enable system wide with '-a' Nick Desaulniers
2022-09-29 22:10 ` Slade Watkins
2022-09-30 3:23 ` Ian Rogers
2022-09-30 4:26 ` Namhyung Kim
2022-09-30 4:31 ` Ravi Bangoria
2022-10-05 21:55 ` Nick Desaulniers
2022-10-05 22:50 ` Stephane Eranian
2022-10-07 3:56 ` Ravi Bangoria
2022-10-11 21:32 ` Nick Desaulniers
2022-10-12 4:06 ` Ravi Bangoria
2022-10-12 5:04 ` Ravi Bangoria
2023-06-23 16:23 ` Nick Desaulniers
2023-06-23 23:18 ` Namhyung Kim
2023-06-26 5:44 ` Ravi Bangoria [this message]
2023-07-10 21:22 ` Nick Desaulniers
2023-07-11 5:14 ` Ravi Bangoria
2022-10-11 21:38 ` Nick Desaulniers
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5c077e61-c206-812f-1cb9-d47785e8176f@amd.com \
--to=ravi.bangoria@amd.com \
--cc=eranian@google.com \
--cc=irogers@google.com \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-perf-users@vger.kernel.org \
--cc=llvm@lists.linux.dev \
--cc=morbo@google.com \
--cc=namhyung@gmail.com \
--cc=ndesaulniers@google.com \
--cc=peterz@infradead.org \
--cc=sandipan.das@amd.com \
--cc=srw@sladewatkins.net \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).